Hand operated multiload grease gun

ABSTRACT

A hand-operated grease gun adapted to use grease in either bulk form or cartridge form includes a grease container having a cylindrical barrel and a cylindrical sidewall of reduced diameter formed integrally with the barrel portion of the container and connected to it by means of a peripheral shoulder which defines a number of curved slots which admit passage through the container wall in an axial direction. A plunger assembly is mounted within the container for reciprocation therein; and it includes a flexible, resilient sealing means for selectively sealing either with the interior surface of the barrel or a grease cartridge, if it is used. Latch members are connected to the plunger assembly for moving with it; and as it is retracted into the rear portion of the container, the latch members pass through the slots in the shoulder of the barrel to extend exterior of and adjacent to the rear cylindrical sidewall of reduced diameter. Each of the latch members includes a laterally projecting finger so that when the plunger assembly is rotated, the latch members hold the plunger assembly in its retracted state for receiving a grease cartridge.

United States Patent [72] Inventor Edwin F. Sundholm 2,815,151 12/1957 Collins 222/327 A l N g z gf City Iowa 50010 Primary Examiner-Robert B. Reeves [2]] Assistant Examiner-Thomas E. Kocovsky [22] Filed Sept 1969 Attorney-Dawson Tilton Fallon & Lungmus [45] Patented Oct. 12, 1971 2 ABSTRACT: A hand-operated grease gun adapted to use grease in either bulk form or cartridge form includes a grease [54] Z g F ISULTILOAD GREASE GUN container having a cylindrical barrel and a cylindrical sidewall aims rawmg of reduced diameter formed integrally with the barrel portion [52] US. Cl 222/309, of the container and connected to it by means ofa peripheral 222/326, 2 8 /23 shoulder which defines a number of curved slots which admit [51] H passage through the container wall in an axial direction. A [50] 222/325, plunger assembly is mounted within the container for recipro- 326, cation therein; and it includes a flexible, resilient sealing /23 means for selectively sealing either with the interior surface of the barrel or a grease cartridge, if it is used. Latch members [56] References Cmd are connected to the plunger assembly for moving with it; and UNITED STATES PATENTS as it is retracted into the rear portion of the container, the 2,790,424 4/1957 Giladett 92/23 latch mb r pas through the slots in the shoulder of the 3,059,980 10/1962 Sundholrn 92/23 arrel to extend exterior of and adjacent to the rear cylindrical 3,430,735 3/1969 Collins 92/23 X sidewall of reduced diameter. Each of the latch members in- 2,361,126 10/ 1944 Klein 222/386 X cludes a laterally projecting finger so that when the plunger as- 2,714,474 8/1955 Sundholm 222/386 m lyi rotated, the latch members hold the p g 2,759,640 8/1956 Deupree 222/326 sembly in its retracted state for receiving; a grease cartridge.

0 I64 I35 I40 165 123 I73 1 64 I48 I36 7 I25 I 150 I200 327 luuun, Hr I73! 167 WI lee C 28 I34 I73 PATENTEU um I 2 Ian INVENTORI WIN P. SU NDHOLM gna ATT'YS iii/:4?

HAND OPERATED MULTILOAD GREASE GUN BACKGROUND AND SUMMARY The present invention relates to hand-operated grease guns that are adapted to receive grease either in bulk form (through pressure loading or suction filling) or cartridge form. More particularly, the present invention pertains to a combination for selectively holding the plunger assembly which reciprocates within the grease container in a retracted position at the rear of the container.

My US. Pat. No. 3,059,980 which issued in 1962 disclosed a mechanism for holding the plunger assembly in a retracted position within the grease container or barrel so that the grease gun is ready to receive grease in cartridge form by inserting a paperboard cartridge of grease within the barrel while the plunger assembly is being held in its retracted position. The structure of that patent included a rearwardly extending guide tube which was provided at its hind edge with a pair of hook-shaped ears. The rear cap of the grease container extends transverse of the access of the container and defines a central aperture through which a plunger rod extends for reciprocating the plunger assembly. The rear cap also defines a pair of curved slots for receiving the ears on the guide tube as the plunger assembly is retracted. The plunger assembly may be locked in its retracted position by rotating the plunger rod which, in turn, rotates the plunger assembly and the guide tube to cause the hooks on the ears at the end of the guide tube to engage the outer surface of the rear cap and lock to it. A coil spring within the container and interposed between the rear cap and the plunger assembly biases the plunger assembly forwardly so that once the ears extend through the rear cap and are rotated, the plunger assembly becomes securely yet releasably held in its retracted position.

The guide tube and hook-shaped ears of that construction are preferably formed from thin sheet stock. When the plunger assembly is being held in its retracted position, the ears of the guide tube stick out from the rear cap of the grease container where they may accidentally be dislodged or, because they are formed of thin sheet metal, be bent or otherwise deformed thereby making it difficult to reinsert the locking cars into the curved slots in the rear cap of the container. Further, these cars form a fairly sharp projecting surface behind the grease container which is undesirable in any hand'operated tool. 1 y

The present invention overcomes the difficulties outlined above although it is not limited to use with that particular structure. In the present invention, the grease container includes a cylindrical barrel portion for receiving grease either in bulk form or cartridge form and in which the plunger assembly reciprocates. At the rear portion of the grease container (i.e., the portion through which the plunger rod extends), the container wall, while still remaining cylindrical, has a lesser diameter than the barrel portion; and between the rear cylindrical wall of reduced diameter and the barrel, there is provided a peripheral shoulder which defines a number of curved slots.

The plunger assembly includes a double-cup plunger of resilient, flexible material which is slidably mounted on the plunger rod. The plunger includes a transverse web integrally molded with forward and rearwardly extending walls or lips for sealing with the interior surface of the barrel or a cartridge, whichever is used. The rear surface of the web is supported by a cup-shaped member having a forward transverse wall contacting the rear surface of the plunger web; and the supporting member is provided with a peripheral, cylindrical flange or skirt which extends rearwardly thereof and is provided with latch members extending axially of the container. When the plunger assembly is properly aligned and retracted, the latch members pass through the slots in the shoulder of the container; and each latch member is provided with a laterally extending finger. Thus, when the plunger assembly is rotated in the proper direction, the fingers extend over the shoulder to hold the plunger assembly in its retracted position. After passing through the slots in the peripheral shoulder of the container, the latch members he adjacent to the rear cylindrical wall of the grease container which has a reduced diameter. Hence, the latch members are protected against accidental dislodgement and deformation. Further, since the latch members are secured immediately adjacent the rear, cylindrical sidewall of the barrel (and preferably are curved in cross section to conform thereto), there are no sharp surfaces projecting from the gun when the plunger assembly is secured in its retracted position.

In a preferred embodiment, namely when used in combination with the above-identified copending application, a deflector member in the form of a cylinder is telescopically received on the cup-shaped support means which supports the rear surface of the plunger web and also includes the latch members; and the deflector cylinder engages the interior surface of the peripheral shoulder of the grease container when the plunger assembly is retracted; and it is interposed between the outer barrel wall and the cylindrical skirt or flange of the latch support so as to guide that support as the latch members pass through their associated slots.

Other features and advantages of the instant invention will be apparent to persons skilled in the art from the following detailed description of alternative embodiments accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.

THE DRAWING FIG. 1 is a side elevational view of a grease gun incorporating the present invention, partially cut away to show the plunger assembly in cross section;

FIG. 2 is a side cross sectional view of the inventive combination showing the plunger assembly in a retracted position;

FIG. 3 is an end view of the grease gun taken through the sight line 33 of FIG. 2;

FIG. 4 is a closeup view of the peripheral shoulder of the grease container, partially cut away to show one latch member;

FIG. 5 is a transverse cross sectional view taken through the sight line 5-5 of FIG. 2;

FIG. 6 is a detailed view of the front of the plunger assembly showing the bayonet latch and housing; and

FIG. 7 is a side cross sectional view of an alternative embodiment of a grease container and plunger assembly in its retracted position which incorporates the inventive principle.

DETAILED DESCRIPTION Referring first to FIG. 1, there is shown a hand-operated grease gun which includes a grease container C, a plunger assembly P mounted within the container C for urging grease contained therein toward the forward (left as viewed in the drawing) end thereof, and a dispensing head designated H. Although it does not form a part of the present invention, the dispensing head l-l includes a cap 10 for threadably receiving the container C, a high pressure cylinder 11, and a housing 12 for an outlet check valve. A piston 13 is connected to a hand lever 14 at an intennediate location 15; and the end of the hand lever 14 is pivotally connected at 16 to a link 17, the other end of which is pivotally connected at 18 to the housing 112. A pipe 19 is connected'to the housing 12 for the outflow of grease to an adapter (not shown). In operation, one hand is placed on the container C and the other hand operates the handle 14 to reciprocate the piston 13 in the high pressure cylinder 11 to force grease through the check valve in the housing 12 and the pipe 19. Grease is admitted into the high pressure cylinder II by means of a port communicating the interior of the cylinder C with the bore of the piston 13 when that piston is retracted. Further details on a preferred dispensing head may be obtained from the copending, coowned application for Dispensing Head for Lever Operated Hand Grease Gun, Ser. No. 854,581 filed Sept. 2, 1969.

The hand-operated grease gun of FIG. 1 is being used in combination with a grease cartridge 20 received in the container C. The cartridge 20 is a cylindrical paperboard container holding grease throughout its length except for a rear portion of about one-half inch to facilitate insertion of the plunger assembly P without spilling. As shown in FIG. 1, the cartridge 20 is in a fully inserted position; and the cap of the dispensing head H is tightly secured to the container C.

A plunger rod a extends axially of the container C and through the back thereof where it is formed into a loop handle 2l. The plunger assembly P is slidably mounted on the rod 200; and urged to a forward position (i.e., toward the dispensing head H) by means of a coil spring 23 interposed between the rear of the container C and the plunger assembly P.

Turning now to FIGS. 1 and 2, the plunger assembly will be described in greater detail. A double-cup sealing member is generally designated by reference numeral 25; and it includes a transverse web 26, a forwardly opening peripheral sidewall or lip 27 and a rearwardly opening sidewall or lip 28. The web 26 defines a central aperture for mounting to a hub 29 slidably and sealingly mounted on the plunger rod 20a. An internal annular groove 30 is formed in the hub 29 for receiving an O- ring 31 to effect the seal. The sealing member 25 is preferably molded from a flexible, resilient synthetic rubber such as neoprene.

A cup-shaped, rearwardly opening support member is generally designated 34; and it includes a transverse, discshaped front wall 35 secured about a central aperture to the hub 29 and engaging the rear surface of the web 26 of the sealing member 25. Depending rearwardly from the forward support member 35 is a cylindrical flange member generally designated 36 and including a front cylindrical flange 37 formed integrally with the periphery of the front wall 35 and having a diameter slightly less than the diameter of the base of the rear sidewall 28 of the sealing member 25, and a second cylindrical flange 38 of slightly larger diameter and connected to the rear circular edge of the forward flange 37 by means of a peripheral connecting portion 39. Depending rearwardly from the outer cylindrical flange 38 are three hook-shaped latch members designated respectively 40a, 40b, and 400 (see FIG. 3). Telescopically received on the rear flange 36 of the support member 34 is a cylindrical deflector member generally designated by reference numeral 42, and including a forward cylindrical flange 43 having a diameter slightly greater than the forward flange 37 of the supportmember 34, a rear cylindrical flange 44 having a diameter slightly greater than the diameter of the rear flange 38 of the support member 44, and a center connecting portion 45 formed integrally with the flanges 43 and 44. The center connecting portion 39 of the rear flange 36 of the support member 34 forms a seating surface for engaging the connecting portion 45 of the deflector member 42 to limit the rearward motion thereof. The forward circular edge of the front flange 43 of the deflector member 42 engages the sealing member 25 at the base of the rear sidewall 28 (that is, along a circumferential area defining the outer periphery of the web 26). When the plunger assembly P is received in a cartridge 20, the deflector member 42 is fully received on the side flange means 36 of the rear support member 34 with its forward circular edge lying approximately in the same plane as the forward wall 35 of the support member 34, as shown in FIG. I. When, however, the plunger assembly is retracted to a rear position, the rear circular edge of the deflector cylinder 42 engages a shoulder in the container C (described in detail below) to force the deflector to telescope forwardly of the support member 34 and into engagement with the periphery of the web 26 to urge the engaged portion of the web 26 to a forward position, thereby forcing the forward sidewall 27 of the sealing member 25 to a contracted position for receiving the cartridge 20, as shown in FIG. 2.

The forward surface of the web 26 is supported by means of a disc-shaped suppon member 48 which is provided with a forwardly inclined peripheral flange 49 for limiting the forward motion of the deflected web 26 (see FIG. 2). The forward support member 48 is also secured to the hub 29. A cupshaped housing generally designated 50 is secured to the forward surface of the disc support member 48; and it includes a central aperture 51 for receiving the plunger rod 200, and side-extending apertures 52 and 53 communicating with the central aperture 51 for admitting passage of bayonet members 55 and 56 (see FIG. 6) within the housing provided by the member 50. The housing 50 includes inwardly fonned stop members 60 and 61 for limiting the rotational movement of the plunger rod 20a relative to the plunger assembly P. When the rod is pulled to a retracted position by means of a handle 21 so that the bayonet members 55 and 56 are received within the housing 50, and the rod is rotated, the plunger assembly P is temporarily secured to the plunger rod 200 and constrained to move with it in an axial direction.

Further details of the plunger assembly including the deflector member may be found in my copending, co-owned application for Plunger Assembly for Multi-Fill Hand Grease Guns, Ser. No. 854,534, Filed Sept. 2, 1969.

Turning now to the grease container C, it includes a cylindrical barrel portion 64 for receiving the cartridge 20 or, alternatively, for receiving and containing grease in bulk form. Toward the rear (right side in FIGS. 1 and 2) of the barrel 40, the container C includes an inwardly inclined surface 65 and an integral, cylindrical guide surface 66 having a diameter slightly smaller than that of the barrel 64. An inwardly turned circular flange 67 is formed at the rear edge of the guide surface 66; and there are three curved slots formed in the flange 67 and designated respectively 67a, 67b, and 67c, for receiving respectively the latch members of the rear support member 34 of the plunger assembly. In the embodiment of FIGS. 1-6, the rear closure for the grease container C is in the form of a forwardly facing, cup-shaped rear cap generally designated by reference numeral 70; and it includes a transverse rear wall 71 defining a central aperture which is provided with a forwardly facing side flange 72 for engaging and guiding the plunger rod 20a. Extending forwardly of the transverse rear wall 71 is a cylindrical sidewall 73 having a diameter slightly less than the diameter of the rear cylindrical flange 38 of the web-rear support member 34. At the forward edge of the sidewall 73 is an annular outwardly extending flange 75 located internally of the corresponding annular flange 67 which is an integral part of the barrel 64; and the annular flanges 67 and 75 are welded together to form a unitary construction. The annular flange 75 of the rear cap 70 defines three curved slots 75a, 75b, and 75c (see FIG. 5) which are 'aligned with the corresponding curved slots 67a-67c described above.

Turning now to FIG. 4, the latch member 400 which extends rearwardly of the outer cylindrical flange 38 of the web-support member 34, includes a rearwardly extending shank 78 and a laterally extending finger 79. In transverse cross section, both the shank 78 and the finger 79 are curved and conform to the curvature of the flange 38 from which they are formed for facilitating their insertion through the slots 75a and 670. Thus, when the plunger assembly P is pulled to its rear position, the latch members 40040:: pass through their associated slots in the annular flange 67 and 75. At the same time, the deflector member 42 engages the forward surface of the annular flange 75 and urges the'peripheral circumferential area of the web 26 forwardly relative to the center of the web to force the forward sidewall 27 of the flexible sealing member 25 to a contracted diameter for receiving the cartridge 20. When the latch members 404-400 thus extend through the sidewall of the container C and the plunger assembly P is rotated by means of the bayonet members 55 and 56 (FIG. 6) the laterally extending fingers of the latch members will be forced over the side edges of their corresponding slots to engage the rear surface of the circular flange 67 and hold the plunger assembly in its retracted position as seen in FIG. 2.

It will be observed that the curvature of the latch members Mia- 16 also conforms to the outer surface of the cylindrical sidewall 73 of the rear cap 70, that the interior surface of the latch members Wu-60c extends immediately adjacent the outer surface of the sidewall 73 of the cap 711, and that the sidewall 73 extends to a rear position beyond the edges of the latch members Mia-4111c even when the plunger assembly is in its mostretracted position. Thus, the latch members ltlwdllc are protected against accidental dislodgement, deformation or bending while holding the plunger assembly in a retracted position; and no sharp surfaces protrude from the cartridge C during this time. When the plunger assembly is being retracted, the rear edge of the cylindrical flange M of the deflector member 62 is guided within the reduced cylindrical portion 66 of the container C by means of the frustoconical surface 65; and this rear flange serves to guide the corresponding rear flange 36 of the support member 3 1 to align the latch members 100-6110 with their associated slots.

Turning now to FIG. 7, there is shown an embodiment which does not employ the deflector member 42. In the description of the embodiment of FIG. 7, for convenience of reference, identical reference numerals preceded by a 1 will identify like elements. Again, the container is designated C and the plunger assembly P. The plunger assembly P is slidably mounted on a plunger rod 126a; and it includes a flexible, resilient sealing member 123 having a forwardly opening front sidewall 127, a rearwardly opening rear sidewall 126 and a transverse web 126. The web is mounted on a hub 129 which is slidably and sealingly secured to the rod 1211a. A coil spring 123 is interposed between the rear surface of the container C and the plunger assembly 1? to urge the latter to a forward position. The rear surface of the web 126 is supported by means of a cupshaped support member generally designated 13% and including a forward wall 133 engaging the rear surface of the web 126, and a rearwardly extending cylindrical flange 136 including a plurality of curved latch members, one of which is designated in FIG. 7 by reference numeral 1410a. The forward surface of the web 126 is supported by means of a metallic disc 166 secured to the hub 129; and a bayonet housing 150 is secured to the disc 1.

The container C includes a cylindrical barrel 1641 within which the plunger assembly P reciprocates; and the sealing member 125 is in sealing engagement with the interior surface of the barrel 1641. At a rear location, the barrel 1641 is tapered inwardly to form an inclined, frustoconical reducing portion 165. integral with the frustoconical portion 165 is a cylindrical intermediate wall 166 having an internal diameter slightly larger than the external diameter of the flange 136 of the support member 1341. An annular limiting flange member 167 is formed inwardly of the rear edge of the intermediate wall portion 166; and a rear cylindrical sidewall 173 is formed integrally with the internal periphery of the flange 167. The rear edge of the sidewall 173 is rounded inwardly as at 1730 to define a central aperture 171%.

A rear cap 171 includes a peripheral shoulder 171a fitting within the rounded portion 173a of the side wall 173 for welding thereto, and a central, cylindrical flange 172 for receiving the plunger rod 1211a. I

When the plunger assembly of the embodiment of FIG. 7 is retracted, the latch members are guided by the frustoconical portion 166 of the barrel 1641 within the cylindrical intermediate wall 166 so that when the plunger assembly is rotated to bring the latch members into alignment with their associated slots formed in the annular flange 167, further rearward motion will pass the latch members through those slots. Further rotational motion of the plunger assembly will then cause laterally extending fingers (similar to the finger 79 as seen in FIG. 1) to pass over the solid portion of the flange 67 and hold the plunger assembly in a retracted position even though the rod 1211a may be released. It will also be observed that when the latch members pass through the sidewall of the container C they remain immediately adjacent the outer surface of the reduced rear sidewall 173 and are protected thereby against deflection or other deformation, and a smooth exterior is presented without projecting sharp edges.

Having thus described in detail alternative embodiments of the present invention, persons skilled in the art will be able to substitute elements equivalent to those disclosed and to modify the illustrated embodiments without departing from the inventive principle; and it is, therefore, intended to cover all such modifications and equivalents as they are embraced within the spirit and scope of the invention.

lclaim:

1. In a hand-operated gun adapted to receive grease in bulk or cartridge form, including a grease container having a forward and a rear end with a cylindrical barrel at its forward end, wherein the improvement comprises: said container defining at its rear end a cylindrical. sidewall of reduced diameter connected to said barrel by means of a peripheral connecting shoulder defining slot means admitting passage through said container in an axial direction; and a plunger assembly adapted for reciprocation within said container and including flexible resilient sealing means for sealing engagement with said barrel, and latch means connected to said plunger as sembly for moving therewith including rearwardly projecting shank means extending axially and rearwardly of said container for passing through said slot means when said plunger is drawn to the rear of said container and extending exterior of and adjacent to said rear cylindrical sidewall of reduced diameter and adapted to selectively lock with said shoulder, said reduced cylindrical wall portion of said container having an axial dimension longer than the axial dimension of said latch means.

2. The structure of claim 1 wherein said grease container further comprises an inwardly inclined frustoconical wall member interposed between said shoulder and said barrel for guiding said latch means into said slot means on said shoulder.

3. In a hand-operated grease gun the combination of a grease container having a forward cylindrical barrel, a rear cylindrical sidewall of lesser diameter than said barrel and said rear sidewall and defining at least one slot admitting passage in a direction parallel to the axis of said container; and a plunger assembly including sealing means for sealingly engaging the interior surface of said barrel and rearwardly extending latch means connected to said sealing means and adapted to pass through said slot in said container and adjacent the exterior surface of said rear sidewall thereof for engaging the exterior surface of said shoulder flange when said plunger assembly is rotated to hold said plunger assembly in a retracted position, said rear cylindrical sidewall of said container extended rearwardly beyond the furthest projection of said latch means and immediately inward thereof to protect. the same against accidental dislodgment or deformation and to prevent the occurrence of projecting edges when the plunger assembly is held in retracted position.

4. The structure of claim 3 wherein said container includes a frustoconical surface between said barrel and said shoulder flange for guiding said latch means into said slot and through said container when said plunger assembly is retracted.

5. The structure of claim 3 wherein said container comprises a first integral part providing said barrel and shoulder flange, and a second integral part providing said rear sidewall of reduced diameter and a transverse end plate defining a central aperture for receiving and guiding a plunger rod on which said plunger assembly is slidably mounted.

6. The structure of claim 3 wherein said container comprises a first integrally formed part providing said barrel, said shoulder flange and said rear sidewall of reduced diameter, and a second part providing a transverse end plate secured to said rear sidewall for receiving and guiding a plunger rod on which said plunger assembly is slidably mounted. 

1. In a hand-operated gun adapted to receive grease in bulk or cartridge form, including a grease container having a forward and a rear end with a cylindrical barrel at its forward end, wherein the improvement comprises: said container defining at its rear end a cylindrical sidewall of reduced diameter connected to said barrel by means of a peripheral connecting shoulder defining slot means admitting passage through said container in an axial direction; and a plunger assembly adapted for reciprocation within said container and including flexible resilient sealing means for sealing engagement with said barrel, and latch means connected to said plunger assembly for moving therewith including rearwardly projecting shank means extending axially and rearwardly of said container for passing through said slot means when said plunger is drawn to the rear of said container and extending exterior of and adjacent to said rear cylindrical sidewall of reduced diameter and adapted to selectively lock with said shoulder, said reduced cylindrical wall portion of said container having an axial dimension longer than the axial dimension of said latch means.
 2. The structure of claim 1 wherein said grease container further comprises an inwardly inclined frustoconical wall member interposed between said shoulder and said barrel for guiding said latch means into said slot means on said shoulder.
 3. In a hand-operated grease gun the combination of a grease container having a forward cylindrical barrel, a rear cylindrical sidewall of lesser diameter than said barrel and said rear sidewall and defining at least one slot admitting passage in a direction parallel to the axis of said container; and a plunger assembly including sealing means for sealingly engaging the interior surface of said barrel and rearwardly extending latch means connected to said sealing means and adapted to pass through said slot in said container and adjacent the exterior surface of said rear sidewall thereof for engaging the exterior surface of said shoulder flange when said plunger assembly is rotated to hold said plunger assembly in a retracted position, said rear cylindrical sidewall of said container extended rearwardly beyond the furthest projection of said latch means and immediately inward thereof to protect the same against accidental dislodgment or deformation and to prevent the occurrence of projecting edges when the plunger assembly is held in retracted position.
 4. The structure of claim 3 wherein said container includes a frustoconical surface between said barrel and said shoulder flange for guiding said latch means into said slot and through said container when said plunger assembly is retracted.
 5. The structure of claim 3 wherein said container comprises a first integral part providing said barrel and shoulder flange, and a second integral part providing said rear sidewall of reduced diameter and a transverse end plate defining a central aperture for receiving and guiding a plunger rod on which said plunger assembly is slidably mounted.
 6. The structure of claim 3 wherein said container comprises a first integrally formed part providing said barrel, said shoulder flange and said rear sidewall of reduced diameter, and a second part providing a transverse end plate secured to said rear sidewall for receiving and guiding a plunger rod on which said plunger assembly is slidably mounted. 